TY  - JOUR
AU  - LIU, Zhiyuan
AU  - LI, Xing
AU  - ZHOU, Xun
PY  - 2023
TI  - Temperature distribution for fire in a forced ventilation subway car
JO  - Journal of Tsinghua University (Science and Technology)
SN  - 1000-0054
SP  - 1529
EP  - 1536
VL  - 63
IS  - 10
AB  - ObjectiveUrban rail transit in China is developing rapidly due to the significant increase in subway lines and passenger flow. Although the subway system provides convenient transportation, the occurrence of subway car fires poses a potential risk to passengers. Subway cars are narrow and enclosed spaces, making them susceptible to significant property damage and casualties in the event of a fire. The existing research on subway car fires is primarily focused on natural ventilation conditions. Notably, subway cars are equipped with air supply systems to provide fresh air during normal operation, which continues to be operational during the initial stage of a fire. This air supply may considerably impact fire development and temperature distribution within the car during the fire. A clear understanding of the spreading of smoke and temperature distribution during subway car fires under air supply conditions can effectively determine the best position for fire detectors within the car.MethodsThis study establishes a comprehensive simulation model of a subway car. The car model comprises three main components: the passenger area, internal seating, and the top air supply system. The car includes four groups of air supply systems on the top. The length, width, and height of the car are 21.82, 2.92, and 1.86 m, respectively. After constructing the car model, we partition the grids and define the boundary conditions based on two ventilation scenarios: with and without a forced air supply. Further, two typical fire source locations—the center of the car and the area below the air supply outlet—and five different fire source powers are investigated. Analysis of this study primarily focuses on the airflow velocity distribution within the car under ventilation, and the temperature distribution within the car under the influence of air supply and different fire source positions.ResultsThe results indicate that airflow vortexes are formed within the compartment when air is supplied, and the vortex position is directly related to the seating arrangement. The airflow velocity distribution within the compartment is significantly affected by the position of the air supply outlet. Under the experimental conditions, the presence or absence of ventilation within the compartment does not have a significant impact on the maximum temperature rise of the car ceiling. This may be attributed to the high temperature near the fire source, which results in significant thermal buoyancy. Hence, the air supply at the outlet does not affect the fire plume significantly. A stable smoke stratification may still occur during the car air supply, although the height of the smoke layer is considerably higher compared to natural ventilation. A strong correlation between the ceiling flue gas temperature and the position of the air supply outlet exists in the presence of the air supply. Each air supply outlet creates a low-temperature area, and the ceiling flue gas temperature at both ends of the compartment is significantly lower compared to natural ventilation. Furthermore, regardless of the presence or absence of an air supply, the smoke temperature on the compartment's ceiling decreases exponentially.ConclusionsThe findings of this research can serve as a reference for establishing subway car fire prevention strategies.
UR  - https://doi.org/10.16511/j.cnki.qhdxxb.2023.22.042
DO  - 10.16511/j.cnki.qhdxxb.2023.22.042